Removable doctor blade holder with lockable mount

ABSTRACT

A doctoring apparatus for doctoring a roll surface comprises a doctor blade, a blade holder for applying the doctor blade to the roll surface, and a doctor back having a support surface on which the blade holder is adapted to slide. A locking bar is subdivided into multiple mechanically interlocked segments and is mounted by fasteners on the support surface of the doctor back for movement lengthwise in opposite directions between locked and unlocked positions. The locking bar is configured and dimensioned to fit loosely within a groove on the underside of the blade holder. In its unlocked position, the locking bar permits the blade holder to slide on the doctor back support surface into and out of an operative position adjacent to the roll surface. In its locked position, the locking bar releasably secures the blade holder in its operative position.

REFERENCE TO RELATED APPLICATIONS

This application claims priority from provisional patent application Ser. No. 60/655,717 filed Feb. 22, 2005.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates generally to doctors used in paper making machines, and is concerned in particular with the provision of a blade holder which is firmly locked in its operative position on the doctor back, and which is readily separable from the doctor back and removable from the paper making machine for cleaning, inspection and repair.

2. Description of the Prior Art

The main components of a doctor system include the doctor blade, the blade holder, the doctor back and the loading mechanism. The doctor blade keeps the roll clean and/or sheds the sheet. It must be substantially flat, straight and parallel, and its composition must be compatible with the roll to be doctored.

The blade holder exerts a uniform, designated load pressure on the blade. It holds the blade firmly against the roll, accommodates roll irregularities and, within limits, compensates for thermal expansion.

The doctor back is in essence the backbone of the doctor. It serves as the support structure for the blade holder. The loading mechanism pivots the doctor back to load the doctor blade against the roll.

Doctor blade holder designs used in recent years are more complex and have more components than the simpler blade holders used in the past. As a result, the more recent holder designs require more routine cleaning and maintenance.

As disclosed for example in U.S. Pat. No. 5,980,692 (Goodnow et al.), it is known to provide removable blade holders which allow for cleaning and maintenance to be performed off line while the paper machine continues to operate with a replacement blade holder.

Experience has indicated, however, that removal of the blade holder is sometimes made difficult due to frictional resistance between mating sliding surfaces.

SUMMARY OF THE INVENTION

The present invention addresses this problem by mechanically interlocking the blade holder to the doctor back with linked elements. The linked elements are strategically positioned to reduce frictional resistance to blade holder removal and replacement. A locking feature is also incorporated.

These and other features and advantages of the present invention will now be described in greater detail with reference to the accompanying drawings, wherein:

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a cross sectional view through a blade holder and mounting assembly in accordance with the present invention;

FIG. 1B is a plan view of one end of the blade holder and mounting assembly;

FIGS. 2A and 2B are end elevational views respectively showing the locking mechanism in the locked and unlocked condition;

FIGS. 3A and 3B are sectional view taken on line 3-3 of FIG. 1A, and, respectively showing the locking mechanism in the locked and unlocked condition;

FIG. 4 is a partial sectional view showing the connection between two linked elements making up the locking bar; and

FIG. 5 is a cross sectional view through an alternative embodiment of a blade holder and mounting assembly in accordance with the present invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

With references initially to FIGS. 1A, 1B, 2A and 2B, a blade holder and mounting assembly in accordance with the present invention is generally depicted at 10 adjacent to a paper machine roll 12. Roll 12 is driven by conventional means (not shown) for rotation about an axis extending in the cross machine direction. The doctor assembly includes a doctor blade 14, a blade holder 16 and doctor back 18. The doctor back is mounted on the paper machine frame for pivotal movement about its axis extending in the cross machine direction parallel to the rotational axis of roll 12. The loading mechanism (not shown) may, for example, include a piston-cylinder unit acting through a lever arm to pivot the doctor back about its axis in order to load the doctor blade 14, against the surface of the roll 12.

A locking bar 20 is attached by means of screws 22 to a forwardly projecting shelf of the doctor back 18. The locking bar extends in the cross machine direction and has a top with laterally projecting shoulders 20 a defining a width “W,” and a narrower leg 18 b projecting downwardly. Thus, the bar 20 has a generally “T” shaped cross-section.

The blade holder 16 has a complimentary generally “T” shaped slot extending along its entire length and forming ledges 24 underlying the shoulders 20 a of the locking bar.

When the blade holder 16 is mounted as shown and in service, its T slot contacts with the T-shaped bar 20 to establish the requisite mechanical interengagement, and to provide guide surfaces during longitudinal removal and replacement of the blade holder.

As shown in FIG. 4, the locking bar is preferably made up of individual elements 20′ that are notched at opposite ends with complimentary mechanically engaged holes 20 c and integral pins 20 d coacting in a male/female interlocked relationship. The individual elements 20′ can be more readily machined, and their interlocked relationship facilitates the task of mounting them on the doctor back.

As can be best seen in FIGS. 3A and 3B, the screws 22 extend through slots 26 in the locking bar segments 20′. The slots have ramped side edges 26′. In FIG. 3A, the locking bar 20 has been shifted to the right, causing the ramped side edges 26′ of the slots to become wedged under heads of the screws 22. This is turn urges the shoulders 20 a of the locking bar segments downwardly against the ledges 24 of the blade holder, which in turn urges the locking bar blade holder 16 downwardly into a clamped position on the shelf of the doctor back. In FIG. 3B, the locking bar has been shifted to the left into an unlocked position at which the screw heads are spaced above the ramped side edges 26′.

With reference to FIGS. 2A and 2B, it will be seen that a key 28 is fixed to a projecting end segment end of the bar by a screw 30. The key has a bifurcated base straddling a nut 32 threaded on a spindle 34 projection from the shelf of the doctor back 18. Rotation of the nut in one direction results in the locking bar 20 being pulled into the locked position, and rotation of the nut in the opposite direction causes the locking bar to be pushed into its unlocked position.

In the embodiment illustrated in FIG. 5, the locking bar 20 is carried on an intermediate plate 36 secured to the shelf of the doctor back 18 by screws 38. Set screws 40 are threaded into a rearwardly projecting flange of the plate 36. The set screws provide a means of imparting micro adjustments to the doctor blade in order to match the surface of the roll. 

1. A doctoring apparatus for doctoring a roll surface, comprising: a doctor blade; a blade holder for applying said doctor blade to said roll surface, said blade holder having a groove on its underside; a doctor back having a support surface on which said blade holder is adapted to slide; a locking bar subdivided into multiple mechanically interlocked segments; fasteners for mounting said locking bar on said support surface for movement lengthwise in opposite directions between locked and unlocked positions, said locking bar being configured and dimensioned to fit loosely within said groove, and, when in its unlocked position, to permit said blade holder to slide on said support surface into and out of an operative position adjacent to said roll surface, said fasteners coacting with said locking bar in its locked position to releasably secure said blade holder on said support surface.
 2. The doctoring apparatus of claim 1 further comprising an adjustment mechanism engageable with one end of said locking bar for shifting said locking bar relative to said doctor back between said locked and unlocked positions.
 3. The doctoring apparatus of claim 2 wherein said adjustment mechanism comprises a threaded spindle fixed with respect to said doctor back, a nut threaded on said spindle, and a key straddling said nut and secured to an end segment of said locking bar.
 4. The doctoring apparatus of claim 1 wherein said fasteners extend through slots in said locking bar segments, and wherein said slots have ramped edges coacting in wedged relationship with said fasteners when said locking bar is in its locked position. 